This invention relates to a start-up circuit for a deflection system.
Various deflection system designs have been utilized in television receivers. More recent designs have utilized an integrated circuit, which includes an oscillator, to provide drive signals to switch the deflection system at a line frequency rate or a field frequency rate. Additionally, many of these integrated circuit designs have included automatic frequency and phase control, pulse shaping and noise immunity circuitry. Due to the number of discrete components eliminated by this type of integrated circuit, deflection system costs have been reduced. Also deflection systems utilizing this type of integrated circuit are more reliable, provide improved system noise immunity and provide for easier deflection system assembly.
Integrated circuits generally must, however, be supplied with a relatively low direct current voltage, for example, in a range of 4 to 12 VDC. Television receivers which are so-called "hot chassis" receivers, that is, do not have a 60 Hz power transformer, frequently drive low direct current voltages such as aforementioned by utilizing a dropping resistor and an appropriate voltage limiting device such as a zener diode. These dropping resistors, however, dissipate considerable amounts of power. The absence of a 60 Hz transformer eliminates the possibility of utilizing a low voltage winding of the transformer for providing low voltage for operating the integrated circuit oscillator assembly.
It is desirable to have the deflection circuit oscillator provide useful drive signals as soon as possible after turn-on of the receiver in order to begin deflection circuit operation as soon as possible. The typical integrated circuit oscillator assembly requires approximately 30 percent of nominal direct current voltage before the oscillator will provide drive signals. In contrast, the typical discrete component oscillator of the type which the integrated circuit replaced required approximately 10 percent of nominal direct current voltage to provide drive signals.
In accordance with the invention, a start-up circuit for a deflection system comprises deflection means, including a first oscillator which produces a first signal, for producing a deflection signal in a deflection winding in response to the first signal. A second oscillator is coupled to the first oscillator for controlling the frequency and phase of the first oscillator when a direct current operating potential is coupled to the second oscillator. Rectifying means coupled to the deflection means and the second oscillator provide the direct current potential to the second oscillator when said deflection signal is being produced.
A more detailed description of the invention is given in the following description and accompanying drawing.